Which of the reactions are spontaneous (favorable)?
a. 2H2O(g)⟶2H2(g)+O2(g) Δ𝐺=457 kJ/mol
b. CH4(g)+2O2(g)⟶CO2(g)+2H2O(l) Δ𝐺=−820 kJ/mol
c. 2Mg(s)+O2(g)⟶2MgO(s) Δ𝐺=−1137 kJ/mol
d. C(s)+H2O(l)⟶CO(g)+H2(g) Δ𝐺=90.8 kJ/mol
e. AgCl(s)⟶Ag+(aq)+Cl−(aq) Δ𝐺=55.6 kJ/mol
f. NH3(g)+HCl(g)⟶NH4Cl(s) Δ𝐺=−91.1 kJ/mol
Reactions are spontaneous if dG is negative.
a. Well, it seems like we have to split up some water molecules. So, it's like forcing two friends to separate and breathe a little fresh air - not really spontaneous, if you ask me. So, not favorable.
b. This reaction involves burning methane, so it's basically like setting a fire. And who doesn't enjoy a good fire? Definitely spontaneous and favorable!
c. Ah, the good old magnesium and oxygen bonding to form magnesium oxide. This reaction releases a lot of energy - it's like fireworks in chemistry land! Definitely spontaneous and favorable.
d. Now, this reaction involves turning coal into a gas. It's like taking a boring black rock and making it into something exciting! So, definitely spontaneous and favorable.
e. This reaction breaks down solid silver chloride into ions. You can think of it as taking away a friend's comfort zone. Not so favorable, I'm afraid.
f. This is like mixing ammonia and hydrochloric acid to form a solid compound. It's like putting two reactive friends together and watching them settle down. Definitely a favorable reaction.
So, in summary, the spontaneous (favorable) reactions are:
b. CH4(g)+2O2(g)⟶CO2(g)+2H2O(l)
c. 2Mg(s)+O2(g)⟶2MgO(s)
d. C(s)+H2O(l)⟶CO(g)+H2(g)
f. NH3(g)+HCl(g)⟶NH4Cl(s)
To determine which reactions are spontaneous (favorable), we need to look at the change in Gibbs free energy (ΔG) for each reaction. If ΔG is negative, the reaction is spontaneous and favorable. If ΔG is positive, the reaction is non-spontaneous and unfavorable.
a. 2H2O(g) ⟶ 2H2(g) + O2(g) ΔG = 457 kJ/mol
The reaction has a positive ΔG (+457 kJ/mol). Therefore, it is non-spontaneous and unfavorable.
b. CH4(g) + 2O2(g) ⟶ CO2(g) + 2H2O(l) ΔG = -820 kJ/mol
The reaction has a negative ΔG (-820 kJ/mol). Therefore, it is spontaneous and favorable.
c. 2Mg(s) + O2(g) ⟶ 2MgO(s) ΔG = -1137 kJ/mol
The reaction has a negative ΔG (-1137 kJ/mol). Therefore, it is spontaneous and favorable.
d. C(s) + H2O(l) ⟶ CO(g) + H2(g) ΔG = 90.8 kJ/mol
The reaction has a positive ΔG (+90.8 kJ/mol). Therefore, it is non-spontaneous and unfavorable.
e. AgCl(s) ⟶ Ag+(aq) + Cl-(aq) ΔG = 55.6 kJ/mol
The reaction has a positive ΔG (+55.6 kJ/mol). Therefore, it is non-spontaneous and unfavorable.
f. NH3(g) + HCl(g) ⟶ NH4Cl(s) ΔG = -91.1 kJ/mol
The reaction has a negative ΔG (-91.1 kJ/mol). Therefore, it is spontaneous and favorable.
Based on the change in Gibbs free energy (ΔG), the reactions b, c, and f are spontaneous (favorable).
To determine which reactions are spontaneous or favorable, we need to look at the Gibbs Free Energy (ΔG) values for each reaction. The sign of ΔG indicates whether a reaction is spontaneous or not.
1. For reaction (a): 2H2O(g) ⟶ 2H2(g) + O2(g), ΔG = 457 kJ/mol. Since ΔG is positive (+457 kJ/mol), the reaction is non-spontaneous or unfavorable.
2. For reaction (b): CH4(g) + 2O2(g) ⟶ CO2(g) + 2H2O(l), ΔG = -820 kJ/mol. Since ΔG is negative (-820 kJ/mol), the reaction is spontaneous or favorable.
3. For reaction (c): 2Mg(s) + O2(g) ⟶ 2MgO(s), ΔG = -1137 kJ/mol. Since ΔG is negative (-1137 kJ/mol), the reaction is spontaneous or favorable.
4. For reaction (d): C(s) + H2O(l) ⟶ CO(g) + H2(g), ΔG = 90.8 kJ/mol. Since ΔG is positive (+90.8 kJ/mol), the reaction is non-spontaneous or unfavorable.
5. For reaction (e): AgCl(s) ⟶ Ag+(aq) + Cl-(aq), ΔG = 55.6 kJ/mol. Since ΔG is positive (+55.6 kJ/mol), the reaction is non-spontaneous or unfavorable.
6. For reaction (f): NH3(g) + HCl(g) ⟶ NH4Cl(s), ΔG = -91.1 kJ/mol. Since ΔG is negative (-91.1 kJ/mol), the reaction is spontaneous or favorable.
Therefore, reactions (b), (c), and (f) are spontaneous or favorable.